NARRATOR: We can't claim we haven't been warned. In 1995,
Muslim rebels from Chechnya directed a TV reporter to a park in central Moscow.
The package she found contained a small amount of explosives and something
else: Cesium-137, a radioactive isotope. This was the first known appearance of
what has become a household word: a dirty bomb.

JOHN ASHCROFT (Attorney General, United States of America): ...an
unfolding terrorist plot to attack the United States by exploding a radioactive
dirty bomb.

VINCE CANNISTRARO (Ex-Chief, Central Intelligence Agency
Counterterrorism): A so-called "dirty bomb" is basically just a
conventional explosive with a radioactive core to it. You're going to broadcast
the radioactivity over the area of the conventional explosive.

In Al Qaeda camps in Afghanistan, there were discovered a number of
documents dealing with the methodology of putting together the most deadly kind
of dirty bomb imaginable.

NARRATOR: What would happen if terrorists were to explode a
dirty bomb in the center of a major city?

MICHAEL LEVI (Federation of American Scientists): Typical wind
speed is about ten kilometers an hour and that's roughly how quickly particles
are going to move.

NARRATOR: Just blocks away, people would go about their
business, unaware of the real danger, invisible and odorless, floating on the
wind.

MICHAEL LEVI: Radioactive material will be deposited on the ground,
inside of buildings, on cars that might move around, on people's clothing.

NARRATOR: For anyone who remains in the area, any health
effects could take decades to appear.

MICHAEL LEVI: Up to about 200 meters from the blast, if the area were
not decontaminated, the risk of cancer would increase by one in ten. Now
the Environmental Protection Agency mandates that contaminated areas be cleaned
up so that there is a risk of, at most, one in 10,000.

I imagine that there would be a very strong debate in the aftermath of a
radiological terrorist attack to determine what area would have to be
decontaminated.

JACK CARAVELLI (Department of Energy): Is it a block, two blocks,
five blocks, ten blocks? At what point do people—even if the government says
they are safe—do they feel that it is safe to return?

NARRATOR: Mass destruction or mass disruption? How much of a
threat does a dirty bomb really pose?

MICHAEL LEVI: It seems ridiculous to think that we might demolish or
abandon chunks of a city, but in some cases that will become our preferred
approach.

NARRATOR: We know terrorists can destroy our buildings. With a
dirty bomb could they force us to do it? Dirty Bomb up next on
NOVA.

Major funding for NOVA is provided by the Park Foundation, dedicated to
education and quality television.

Science: it's given us the framework to help make wireless communications
clear. Sprint is proud to support NOVA.

And by the Corporation for Public Broadcasting, and by contributions to your
PBS station from viewers like you. Thank you.

NARRATOR: The dirty bomb is perhaps the least understood of
all terrorist weapons. We have all heard of it, but few of us know what it
would do or what it wouldn't. It's often called the poor man's nuclear weapon,
but that's misleading.

JACK CARAVELLI: A dirty bomb is not a nuclear weapon, but it is a real
threat. It is a weapon that could wreak havoc in ways far beyond its physical
consequences. And that makes it an ideal terrorist weapon.

NARRATOR: The aim of a real nuclear bomb is mass destruction.
Just one can destroy an entire city, as the world saw in Hiroshima and Nagasaki
at the end of World War II. It took enormous scientific expertise, as well as
specially refined uranium and plutonium, for the U.S. to build these early
bombs. Only a handful of countries have managed to follow suit.

A nuclear bomb is still difficult and expensive to build, but a dirty bomb
is not.

JACK CARAVELLI: In many ways it is low tech, and that is one of the most
concerning things. The dirty bomb really is not a major technical challenge.

NARRATOR: That's because a dirty bomb is just ordinary
explosives mixed with something radioactive.

VINCE CANNISTRARO: There is no technological secret to making a dirty
bomb. It just requires the knowledge of making a conventional bomb. All you
need to do to make it a dirty bomb is to add some kindradioactive material.

NARRATOR: The technical term for a dirty bomb is "radiological
dispersal device." It disperses radioactivity—invisible, frightening and
misunderstood.

STEVE JACKSON (Cambridge University): There are many reasons why
people are frightened of radiation. We know it's very harmful, and yet we can't
see it, we can't smell it, and we can't feel it.

NARRATOR: For terrorists, it is that fear of radiation that
makes a dirty bomb so attractive. In the spring of 2002, the word "dirty bomb"
burst into headlines around the world.

JOHN ASHCROFT: We have disrupted an unfolding terrorist plot to attack
the United States by the, by exploding a radioactive dirty bomb.

NARRATOR: Jose Padilla is an American citizen, a former Latino
gang member who converted to Islam and joined Al Qaeda.

VINCE CANNISTRARO: Jose Padilla apparently went to Al Qaeda and said,
"Look give me some money, and I'll carry out an operation for you, including a
dirty bomb."

Al Qaeda said, "Okay, fine." And they gave him $10,000. It was one of the
kinds of operations that Al Qaeda has been known for in the past, kind of a
venture capital, seeding operation.

NARRATOR: The FBI received a tip-off from a captured Al Qaeda
member and was waiting when Jose Padilla landed in Chicago carrying $10,000 in
cash.

Accused of being an enemy combatant, Padilla was placed in a Navy brig
without trial. No evidence against him has been presented in court. Some
question whether Padilla did more than talk about dirty bombs.

But there is other evidence that Al Qaeda is getting ready to act. In the
fall of 2001, as American-led forces took control of Afghanistan, a discovery
was made. Inside a building once used by Al Qaeda were some papers. They
contained research on a new weapon of terror.

VINCE CANNISTRARO: One of these documents spells out in very great
detail how to make a dirty bomb. The understanding was basically at a fairly
advanced physics level. It is a pretty well thought out scenario, on how to
make the most deadly kind of dirty bomb imaginable.

NARRATOR: British intelligence recently reported that Al Qaeda
might have gone beyond the planning stage to actually build a dirty bomb in
1999. No one knows where it went, or how powerful it might be.

A dirty bomb can be tiny; maybe a single stick of dynamite. It's the
radioactive heart, not the explosive, that matters most.

Radioactivity comes from inside nature's tiniest building blocks.
Some atoms of some elements are unstable and that's where the danger
lies.

Every single atom can be thought of as a tiny solar system: electrons orbit
a nucleus made up of protons and neutrons. Because protons all carry a positive
electrical charge, they repel each other. In most atoms, there are enough
neutrally charged neutrons to balance them out and hold the atom together.

But a radioactive atom is unbalanced. It will throw off or absorb particles
until stability is achieved. Those subatomic particles and powerful rays of
energy given off in the process are called radiation. Some radiation, such as
gamma rays and X-rays, can pass right through solid substances, including the
human body.

If radiation pierces living tissue with enough energy, it can knock loose
electrons from the molecules that make up our bodies. This ionization can
trigger all sorts of damage to cells and to DNA, the software that controls
cells. If the parts of DNA that control cell division become corrupted, the
cell might mutate and multiply out of control like these skin cancer cells. A
potentially deadly malignant tumor is born.

Much of what we know about the health effects of radiation comes from
studying the atomic blasts in Hiroshima and Nagasaki. Those who survived
suffered an elevated incidence of leukemia, breast and other cancers years
later. But most of them had been exposed to very high doses of radiation.

What about low levels of radiation, as might come from a dirty bomb? Some
say that any radiation, even tiny amounts, can cause cancer.

STEVE JACKSON: Radiation's a very strange thing because, potentially, a
very small amount of radiation could lead to changes that, for example, could
trigger cancer in the long term. All you really need for a disease such as
cancer is for one cell to go wrong.

NARRATOR: But other scientists disagree. And the epidemiology
of cancer is tricky, because cancer has so many causes.

ANDREW KARAM (University of Rochester): It may take decades for
cancer to appear. And then the probability that the cancer was caused by
radiation, instead of something else, is so low that you just can't
definitively say that, "This man's leukemia was caused by his occupational
exposure to radiation, while this woman's leukemia was something that would
have happened anyhow."

There is no doubt that radiation can cause cancer. The doubt is what level of
radiation it takes to cause cancer.

CHARLES D. FERGUSON (Center for Nonproliferation Studies): The
scientific community, in some respects, is kind of all over the map. A few
scientists say there's a so-called "hormesis effect," which means that for low
levels of radiation, it's good for your health. And so you have from one
extreme to another.

NARRATOR: The risks of low-level radiation are fiercely
debated, but there's no question that high levels are dangerous.

So could terrorists get a powerful enough radioactive source to build an
effective weapon? Dr. Abel Gonzalez is the world's first line of defense
against the dirty bomb. As head of radiation security at the International
Atomic Energy Agency, a bureau of the United Nations located in Austria, his
task is to monitor all types of radioactive material, around the globe. It is a
much harder job than tracking weapons-grade material, like plutonium.

DR. ABEL GONZALEZ (Head of Radiation Security, International Atomic
Energy Agency): Following Hiroshima and Nagasaki there was a big effort
in the world to keep nuclear materials like plutonium and
uranium, very, very well under control. This has not happened with radioactive
material, with low-grade material. It was not felt that this was needed.
Everybody knew that you could not do a nuclear weapon with this. Why to
have that control?

NARRATOR: In December 2001, Gonzalez received troubling news.
A situation had arisen that would ultimately show just how real the threat of a
dirty bomb might be.

ABEL GONZALEZ: I received a telephone call from the head of my emergency
unit, saying to me, "Look, something is going on in Georgia."

NARRATOR: Reports from this remote corner of the former Soviet
empire said that two men were in the hospital with terrible radiation burns.
They had spent a night deep in the Georgian forest beside some small, warm,
metal canisters.

ABEL GONZALEZ: That was the first flash that we got there could
be a serious problem of sources.

NARRATOR: Unlike cancer, which takes years to develop,
radiation sickness appears within hours after exposure to extremely high
doses.

STEVE JACKSON: Radiation sickness has a number of features: hair loss,
sickness, vomiting. And this is really because the cells in various organs in
your body have sustained very high levels of radiation, damaging the DNA and
other components of the cell to such a degree that those cells are actually
dying. And if radiation sickness is bad enough, that leads to you dying, as a
human being.

NARRATOR: What could have caused such injuries? Any source
strong enough to produce radiation sickness like this must be very strong
indeed.

ABEL GONZALEZ: I was convinced that my people either had
drunk too much vodka or that they had made a mistake. For we were absolutely
convinced it was impossible that the source of such an amount of activity would
exist.

NARRATOR: An international task force was assembled to find
out what had burned the woodcutters and to recover the radioactive sources
before they could fall into the wrong hands.

JACK CARAVELLI: The sources exist in regions of real political
instability, where we know that terrorist organizations operate. That
really leads us to try to secure those as quickly as we can.

NARRATOR: The two woodsmen said that they had encountered the
metal canisters on a remote mountaintop, accessible only by a narrow dirt
track. When the task force located the objects, they were lodged behind some
rocks. Radiation detectors indicated that the cylinders contained concentrated
strontium-90, which emits beta radiation.

Beta radiation is a spray of fast-moving electrons that can pass through
thin layers of material, including skin. When beta particles interact with
matter, they generate an intense heat. Strontium-90 metal has been known to
spontaneously ignite.

The metal cylinders were hot enough to melt snow. And small wonder, because
each one contained a substantial percentage of all the strontium spewed out
across Europe during the Chernobyl accident.

ABEL GONZALEZ: For me this was really shocking because I knew the amount
of contamination that the Chernobyl accident has created.

NARRATOR: The explosion of Chernobyl's nuclear power plant
released huge amounts of strontium-90, iodine-131 and other radioisotopes,
forcing the permanent evacuation of hundreds of square miles in the Ukraine.
Scientists are still trying to calculate the full public health impact,
especially far away from the initial blast, where radiation levels were low.

CHARLES FERGUSON: We have good data that a number of children, maybe at
most 2,000 children, developed thyroid cancer as a result of Chernobyl. But
then when you try to look at how many leukemia cases arose from Chernobyl, it's
still unclear how many there are. It happened in 1986. So it could take several
more years, another decade or so for some of these leukemia cases to
show up.

NARRATOR: To protect the recovery crew from direct exposure to
this strontium-90, scientists calculated that no worker should spend more than
40 seconds near the canisters. When the whistle blows, a replacement is sent
in. It took 25 men, working in these short shifts, to secure the deadly
canisters inside a lead-lined drum.

ABEL GONZALEZ: For me it was very nervous time until my people called me
and said the source was secure.

NARRATOR: Back in Vienna, Dr. Gonzalez scoured scientific
literature, trying to find information about these powerful radioactive
canisters. In an obscure Soviet manual, dated 1983, he found plans for a kind
of generator that could run for decades without refueling. Placed in remote
locations these canisters could power lighthouses and navigational beacons for
airplanes. They were fueled by pure strontium-90, producing an internal
temperature of over 800 degrees and converting that heat into
electricity.

ABEL GONZALEZ: This was opening a Pandora's box. What is all this about?
How many we have of these? From where we can get information?

NARRATOR: It quickly became clear that the Soviets had built
thousands of these generators. It meant the ingredients for a dirty bomb were
all over the former Soviet Union.

Atomic Agency inspectors turned up other strange devices. Mounted on
trucks, these objects were part of a vast and forgotten attempt to make Soviet
farming more productive. Blasting seeds with radiation stopped them from
germinating, allowing them be stored longer. The substance that produced the
radioactivity in these devices was cesium chloride. This material does not
exist on earth naturally. Humans create it in nuclear reactions.

CHARLES FERGUSON: Nuclear reactors produced a lot of cesium-137. That's
a particularly dangerous material. It poses an external health hazard. It has a
radioactive half-life of some 30 years so it's around for a long
period of time.

NARRATOR: Cesium-137 emits gamma rays: packets of pure energy
travelling at the speed of light, even through clothes and skin. And for anyone
building a dirty bomb, cesium chloride has one other especially attractive
feature.

NARRATOR: Powdery material is exactly what a terrorist intent
on contaminating a large area would want.

ABEL GONZALEZ: You know what happens in your home if you open a talc
powder box. After a few hours you will have talc all over your home.

NARRATOR: U.N. investigators have established that the former
Soviet Union is littered with forgotten cesium chloride. Unfortunately, no one
knows whether any of it has already fallen into the wrong hands.

So how much damage could a bomb using Soviet cesium chloride actually do?
To find out, a team of scientists has devised a hypothetical dirty bomb
scenario.

GRAHAM SMITH (Enviros: The kinds of factors that we have to consider,
or build into this scenario are...

MICHAEL LEVI: The technical threshold here is much lower.

GRAHAM SMITH: ...which radio nuclide it is.

MICHAEL LEVI: This is the kind of challenge that we could be facing.

NARRATOR: Enviros is a British consulting firm that assesses
environmental risks for governments and nuclear industries around the world.
They have put together a model for a fictional explosion. The results were
cross-checked by American experts.

MICHAEL LEVI: The typical wind speed is about 10 kilometers an hour.

GRAHAM SMITH: In the air, an obvious question is, what's the weather
like?

NARRATOR: In this fictional scenario, the dirty bomb contains
ten pounds of plastic explosives and 74,000 gigabequerels of cesium chloride.
That's the contents of just one Soviet seed-irradiating device—just a handful
of powder, but highly concentrated.

The target? Trafalgar Square, the traditional heart of London. The
terrorists are driving the van. They're already suffering from the effects of
radiation sickness. They didn't bother to shield themselves while handling the
cesium that went into the bomb. But if we know one thing about Al Qaeda, it's
that the fear of death is no deterrent.

VINCE CANNISTRARO: When a group is willing to die handling this kind of
material then there really aren't any limits on their ability to carry out a
nightmare scenario.

NARRATOR: The blast could kill perhaps 10 people immediately,
including the terrorists. But the true threat of a dirty bomb lies in what
would happen next.

GRAHAM SMITH: The simple buoyancy of the air that's been heated by the
explosion may carry the radioactive material perhaps tens of meters up
into the air.

NARRATOR: Loaded with billions of tiny radioactive particles,
the heated air would very quickly begin to spread beyond Trafalgar
Square.

GRAHAM SMITH: If we're talking about wind speeds of meters per
second, five meters per second perhaps, then to go 100 meters,
that's 20 seconds; to go a kilometer, that's only a minute or so.

NARRATOR: Within two minutes the radioactive plume has
traveled about 10 blocks, past government buildings to the Prime Minister's
house. In another minute it will cross the Thames River. It will take just half
an hour for the cloud to reach London's suburbs, six miles east.

GRAHAM SMITH: We've got contaminated air moving across a section ofLondon and, in general, nobody would be aware that thatcontamination was there.

NARRATOR: As the smoke cools, specks of dust and ash would
lose their buoyancy and fall. The cesium chloride would bind with moisture in
the air and with the falling particles. People on the ground would be unaware
of the gathering danger around them.

The good news is that there would be few immediate health problems. The
radioactivity in this hypothetical dirty bomb would disperse so quickly that no
one is likely to get a strong dose. Any radiation sickness—vomiting, burns,
hair loss—like those Georgian woodcutters is highly unlikely.

Instead, Londoners will face a different problem, a long-term one: the
radioactive contamination, in varying degrees, within their city. Particles
will lodge between paving stones. Tiny amounts of cesium will remain in the
grass and soil. Unless it's cleaned up, this radioactivity will stay in place
for decades.

The levels would be highest right at ground zero. Within 200 yards of the
blast, radioactive contamination would reach 160 millisieverts per year.

STEVE JACKSON: We're already talking about very significant
increases in radiation here. This is 80 times the normal background
level of radiation.

NARRATOR: When calculating the risks of radiation, scientists
take as their starting point the natural background radiation we receive every
day, from cosmic rays, from trace uranium under our feet, from potassium in the
food we eat.

ANDREW KARAM: Right now, I've got my radiation meter turned on, and I'm
just holding this out in air because it's measuring all of the radiation that's
in this room from natural sources. Some of that is potassium-40 from the
potassium in our bodies. One one-hundredth of a percent of potassium is
naturally radioactive. That's the second largest source of background radiation
for any of us. Radiation and radioactivity are part of our environment. We
evolved to live with it.

NARRATOR: Our bodies have natural defenses against radiation,
but most scientists agree that levels 80 times higher than normal could easily
overwhelm them. There is little controversy about levels of radiation this
high. If the contaminated area is not cleaned up, anyone who stays could
receive added damage to their DNA.

GRAHAM SMITH: The problem that would arise would be that in the
longer term these people would have an increased risk of cancer due to thatradiation exposure.

NARRATOR: Every day spent in the target area could mean more
DNA damage and more risk of cancer.

STEVE JACKSON: A very important thing to bear in mind about cancer is
that it is a disease that evolves over time. And in order for a cell in your
body to become fully cancerous, it's got to accumulate multiple mutations. Low
levels of radiation over a considerable period of time can slowly, gradually
cause those mutations to take place.

NARRATOR: Using a standard formula, it is estimated that
radiation levels of 80 times background could lead to one case of cancer for
every seven people who continued to live and work here. If the contamination
were heavy enough, there might be a cancer time bomb ticking away in Trafalgar
Square.

STEVE JACKSON: And I think it would be very difficult to justify
individuals being exposed to that kind of additional risk on a day-to-day
basis.

GRAHAM SMITH: Under these circumstances it's quite clear that the
contamination would have to be cleaned up.

NARRATOR: Cleaning up radioactive contamination is possible,
but it's not easy.

Abel Gonzalez watched the process first hand, fifteen years ago. Brazilian
scrap merchants stole a metal box from a hospital and got more than they
bargained for. It contained a small amount of highly concentrated cesium
chloride.

ABEL GONZALEZ: When they cut the source and the powder got out, then the
contamination problem had started.

NARRATOR: The radioactive dust was tracked throughout Goiania.
Nearly two hundred people were exposed. Four would die, including a
four-year-old girl who ate a sandwich after playing with the blue powder. She
was buried in a lead coffin in a grave sealed in concrete.

Pavements, squares, shops and bars needed to be scrubbed and scraped.
Contaminated soil had to be dug up and carted away. Some homes that couldn't be
cleaned were taken away, piece by piece. Decontamination took six months, but
cleaning up the city created a whole new problem.

MICHAEL LEVI: You don't get rid of radioactivity, you just transfer it
to a different material, so whatever it was transferred to, whether it would be
water or some kind of a cloth, would have to be disposed of still in the way we
dispose of radioactive waste.

ABEL GONZALEZ: The radioactive material that created the 5,000 cubic
meters of waste was a capsule of this size, a few centimeters.

NARRATOR: Multiply this mess by a thousand or two to get an
idea what would happen after an intentional release in London.

MICHAEL LEVI: A dirty bomb incident using the same radioactive material
would produce a much larger contaminated area and a much larger amount of
waste, simply because in the Goiania case there wasn't even the intent to
spread the material widely. In the dirty bomb that would be precisely the
point.

NARRATOR: Our hypothetical dirty bomb would spew radioactive
contamination over many square miles far beyond Trafalgar Square. But as we
move away from ground zero, the cesium particles from the dirty bomb would be
more dispersed, and the radiation levels lower. Three miles from the blast,
radiation levels would fall to just 50 percent above normal background.

There is serious disagreement whether radiation levels this
low would cause any health problems, and about how massive a cleanup
effort would be warranted.

ANDREW KARAM: Right now we just do not have definitive data to tell
whether or not small levels of radiation are harmful, harmless or beneficial.
In the absence of that information, I think that it's maybe not good policy to
be trying to reduce radiation levels to meet a risk when we don't even know
where the starting point is.

NARRATOR: But current international safety standards are
designed to save lives at any cost. They are based on the cautious assumption
that even tiny amounts of radiation can cause cancer. Those standards would
require much of London to be decontaminated. And that's not all.

MICHAEL LEVI: In some cases, either the cost or the technical barriers
will be prohibitive to decontaminating an area, and if people aren't willing to
accept the radioactivity in that area, the only feasible option will be to
abandon that space.

It seems ridiculous to think that we might demolish or abandon chunks of a
city, but in some cases, it may simply be that that may become our choice, that
will become our preferred approach.

CHARLES FERGUSON: In the aftermath of a dirty bomb attack, on television
the next day it's going to be non-stop contentious debate. You're going to have
scientists and experts on both sides of the issue. One side saying that if its
low-level contamination, we might not have to actually tear down buildings, as
maybe the guidelines would recommend us doing. And other people are going to
say, "Yes, we've got to follow these strict guidelines. We need to, need to
tear down the buildings." And you're going to have people in between trying to
sort this out, trying to weigh the cost versus the benefits.

NARRATOR: In the United States, the Nuclear Regulatory
Commission is one of the agencies that sets the guidelines.

RICHARD MESERVE (Chairman, Nuclear Regulatory Commission): The
reality is, I think there has to be some balance of cost and benefits. And I
think you could set some guidelines for the decision, but I think it would be
inevitable that in the real world situation...that you'd have to have some
flexibility to exist as the conditions as you find them. If you were to
discover that the cost to reach a particular clean up level were truly
extraordinary you may well conclude, "Well, we'll explore some other
option."

CHARLES FERGUSON: But let's imagine a dirty bomb event occurs let's say
tomorrow, and the government says, "Well, now we're going to change the
guidelines." I can imagine the public would cry foul and say, "Wait a minute,
you're moving the goal post on us." And now you're saying, "Uh, no, no you
know, we don't want to spend that kind of money actually for cleaning
things up."

One thing we need to do is to have this debate now, before there's any kind of
dirty bomb event, to see if we can perhaps reach some consensus. I don't know
if consensus is possible at this stage, but I think a debate, a dialogue is
always healthy.

RICHARD MESERVE: We have found it very hard to have rational discussions
about nuclear materials.

NARRATOR: Demoralizing, divisive debates in the aftermath of a
dirty bomb will only work to the terrorist's advantage. Perhaps the best way to
keep this scenario from becoming reality is to keep radioactive material out of
the hands of those who mean us harm.

The American government is starting to work on the problem. U.S. borders
are watched more closely now than last year. Ships are being searched, and
sophisticated detection equipment is being installed in some ports and other
entry points.

But not all radioactive material comes from outside the country. There's
plenty of it right here.

JACK CARAVELLI: It's not just Russia, let's put it that way. We
certainly have responsibilities and problems in our backyard.

NARRATOR: In March 1998, the people of Greensboro, North
Carolina, woke up to what they thought was a perfectly normal spring day. Tim
Rice, C.O.O. of a general hospital here, set off for work with a busy schedule
of meetings ahead of him. But it got busier than he ever could have imagined.

TIM RICE (Chief Operating Officer, Moses Cone Health System): I
got interrupted from this meeting that I was in, and so I knew it
was something important. One of my physician colleagues said, "Tim, the cesium
is missing." And I kind of sit there and scratched my head and thought, "What
is the cesium? What do we use it for? Is this a real big deal?" And
as I could hear in his voice, he was very concerned and very disturbed.
And that was my first inkling that I've got a problem here. And from
there on, things started to really roll quickly.

NARRATOR: The missing cesium was inside nineteen tiny metal
containers, called brachytherapy needles. These needles are inserted into
tumors. Because doctors know that radiation can kill cells, they focus its
destructive power directly onto cancer cells.

TIM RICE: We were trying not to frighten people, but we were walking
around the facilities with Geiger counters. We were going room by room, through
the basements, through the crawl spaces, just everywhere we could think
of that it could be.

MARION EADDY: We surveyed the main sewer lines running out of the
hospital, and then we began to branch out from there.

NARRATOR: Department of Energy helicopters were called in.
They employed special devices capable of sensing tiny amounts of radioactivity,
even inside buildings or cars.

MARION EADDY: We had the aerial monitoring, flying low, checking out the
remainder of the city, the waste water treatment plants, the land fills.
We had everything but boats.

NARRATOR: The Greensboro hospital's cesium needles were never
recovered. But the experience has led to an entirely new attitude toward
security.

TIM RICE: At the time of this theft, and I'm saying theft
because I presume that's what it was, we were securing this in order
to protect employees or anyone from inadvertently being
exposed to this radioactive material. After that point, we completely changed
our mentality about all of our nuclear substances and secured them in a
fashion to protect anyone from being able to steal them. Today people
ask, "Where's the cesium?" And I won't tell them.

NARRATOR: The missing brachytherapy needles from Moses Cone
Hospital have joined 30,000 other items on a list of radiation sources now lost
inside the U.S.

ANDREW REVKIN (Science Reporter, New York Times): One of the
paradoxes in this situation we find ourselves in now is that we're surrounded
by these sources. We need them. You can't take an X-ray without radiation.

NARRATOR: Ironically, we're relying on radiation more now, a
result of increased security. One source is the X-ray tubes used to screen
luggage at airports - but these only generate radiation when they're plugged
in.

Because radiation can destroy microbes, the U.S. Postal Service is now
employing gamma rays to kill anthrax and other dangerous biological weapons
that might be lurking in the mail. This same technology has already been used
for killing germs in many consumer items.

ANDREW REVKIN: Many states now have irradiation facilities for
sterilizing products. Whether it's a Band-Aid®, whether it's
food, we're becoming, if anything, more dependent on these things in our daily
lives.

CHARLES FERGUSON: It's estimated that in the United States alone, there
are some 2,000,000 radioactive sources, and we need to realize that only a
small fraction of those, maybe on the order of 200,000, actually present
a high security risk.

NARRATOR: Local and federal authorities are now trying harder
to track radioactive material that might pose a dirty bomb threat. New
instruments are being employed to detect radioactivity inside trucks on the
nation's highways. Detection devices have also been quietly installed at
certain entry points into our major cities.

ANDREW REVKIN: We found, in talking to doctors around New York City,
that they're starting to hear from cancer patients who had treatments thatinvolved radiation implantations that kind of thing, so they're slightly
radioactive, slightly, ever so slightly. And there was a car stopped, coming in
through one of the tunnels into the city, just a month ago, because the police
detected radiation in the car. And it was a woman who had recently had cancer
treatment. We're watching. The police are monitoring tunnels for traces of
radioactivity.

NARRATOR: Detectors are also installed in many scrap yards.
That's how authorities found this industrial gauge that had been thrown in the
trash.

MARION EADDY: They are used in industrial settings for measuring
densities of materials or levels of liquids or other materials in tanks, for
determining whether or not the right number of cans is in a case, those sorts
of things.

NARRATOR: Such gauges commonly contain cesium chloride powder,
but one thousand times less than a Soviet seed-irradiating device.

How much damage could such a small amount of radioactive material cause?
Our scientists have constructed another hypothetical scenario to find
out.

In this fictional scenario, the terrorists simply mix the small amount of
cesium found inside the industrial gauge with powder from a
store-bought firework. The target is Washington D.C.'s Metro, used by half a
million commuters every day.

There is a small flash beside the track in one of the tunnels, as the
mixture ignites. Almost immediately, a highly effective dispersal mechanism is
at work: the trains. They push radioactive particles down the track towards
commuters.

MICHAEL LEVI: There won't be any immediate signs that the dispersal of
radioactive materials has occurred. We can't see or hear or taste them.

NARRATOR: But the cesium particles would quietly continue to
spread. Radioactive dust would enter subway cars as the doors open.

MICHAEL LEVI: People could track them on their feet, underneath their
shoes. Trains could move them actively between stations.

NARRATOR: While some particles would be carried on to the next
stop, others would move out of the station via the Metro's ventilation system.

How much of a health threat would this pose? The typical commuter would
receive twice the background dose they get in the course of an average year but
only for a short period—an average of 15 minutes. That translates into a small
increase in their cancer risk, just one in four thousand by standard,
conservative estimates.

MICHAEL LEVI: Individual riders are unlikely to be affected even if the
material remains there for several hours without being disclosed, simply
because any one person doesn't spend all that much time in the station.

NARRATOR: But it might be worse for the staff. After an 8-hour
shift, their cancer risks could rise by one in a hundred.

STEVE JACKSON: They would have to be carefully monitored, and I'm
sure they'd actually want to be monitored for a considerable period
afterwards.

NARRATOR: Scientists agree that these health risks are
manageable. But the psychological factor may be another story.

REPORTERS VOICES: City authorities said they were urgently trying to
establish the...

...scope of the scale of radioactive contamination...

NARRATOR: When news of the attack breaks, people in
Washington, D.C. would be desperate to know the extent of the
contamination.

JACK CARAVELLI: The news media comes on and says a small device has
exploded in Washington. What is the reaction of the populace? How do you
control that? What do you say to them? Do you say a lot? Do you say very
little?

ANDREW REVKIN: I think, initially, people would get the hell out.
Emergency workers would have to deal with the real peril from just
panic. And that's something that presumably, hopefully, city emergency planners
are working on right now...is how do you deal with that?

CHARLES FERGUSON: You'd probably have more deaths due to traffic
accidents than due to ionizing radiation.

NARRATOR: It could be hard for authorities to provide answers
as fast as people want. Contamination could be patchy, high in some parts of
the Metro, low in others, making it difficult to be sure immediately how
serious the attack had been.

JACK CARAVELLI: It may be unclear, for perhaps some period of time,
exactly what the radioactivity was, how much there was of it.

NARRATOR: And that short period of uncertainty could be enough
to fuel our fears.

ANDREW KARAM: The purpose of a dirty bomb would be to terrorize
people, and the reason why people will be terrorized will be
because they think that an incredibly small amount of radiation can give
you cancer.

JACK CARAVELLI: I don't know that people would make the distinctions
between a small radioactive source and a larger radioactive source. Those
distinctions may be totally lost on the population. So, for that reason, even
the smallest of radioactive sources, if used in a dirty bomb scenario, could be
very disruptive.

NARRATOR: The cesium chloride released in Brazil was an amount
similar to that in our subway scenario, enough to fill a cigarette lighter. But
crowds of fearful residents took to the streets.

ABEL GONZALEZ: It became a soup of panic.

NARRATOR: More than 100,000 people—10 percent of the city's
population—filled a stadium and demanded radiation screening.

ABEL GONZALEZ: Everybody wanted to be monitored. Even if you said to
them, "Don't worry, you were very far away; there is no chance," they said,
"No, no, I want to be monitored."

CHARLES FERGUSON: Apparently the press inflamed some fears. They
convinced some of the public that water supplies were perhapscontaminated. It turns out they likely were not, so that led
to even more people wanting to be monitored.

NARRATOR: It turned out that only 200 people had been exposed,
but hospitals and clinics were still swamped.

American experts are now trying to draw lessons from Brazil to help us
prepare for the repercussions of even a small dirty bomb.

MICHAEL LEVI: Ten percent of the city's population demanded screening
for exposure to radiation. Those kinds of things are likely to overwhelm our
public health system. If 10 percent of Washington shows up at the
hospital, you've got some things to confront.

NARRATOR: Current U.S. regulations would require a thorough
decontamination of Metro stations, tunnels and trains, to make them safe for
employees and to calm public fears.

MICHAEL LEVI: We would shut down the subway in order to carry out the
cleanup, and that would result in massive inconveniences and economic losses.
Tourism could be affected. Trade could be affected. The losses could drive into
the tens or hundreds of billions of dollars.

NARRATOR: Maybe this is the real threat from a dirty bomb. It
may hurt few if any. If cleaned up, it may not cause a single case of cancer.
It is not a weapon of mass destruction. But it would still frighten us, and
cost us lots of money, and that makes it an attractive tool of terror.

MICHAEL LEVI: Radiological terrorism can leverage public fear of
radiation to take what would normally be considered a very small amount of
radioactive material, something not all that dangerous, and turn it into
a weapon that can have massive psychological and economic impact.

NARRATOR: A dirty bomb is, above all, a psychological weapon.
But can we use that knowledge to avoid panic and to plan for the attack that
may lie in our future?

RICHARD MESERVE: One of the important things that I recognize in this
job at the Nuclear Regulatory Commission is the reality that people are afraid
of things nuclear. That means that we have to make an effort to deal with the
reality that the public has those concerns and try to make sure that our
processes are as open as possible and that the reasons for our decisions are
made available to the public, so that there isn't a concern that decisions that
adversely affect people are made behind closed doors.

ANDREW REVKIN: We, as a society, should be trying to educate each other.
The more we can be going through that thought exercise now, the better off
we'll be when something happens. And inevitably something will happen, whether
it's radiological, biological, chemical, something will happen.

NARRATOR: What is the U.S. doing to protect itself against
this threat? On NOVA's Website, hear what one of the nation's leading experts
on nuclear terrorism has to say, at PBS.org or America Online, Keyword
PBS.

To order this show, or any other NOVA program, for $19.95 plus shipping and
handling, call WGBH Boston Video, at 1-800-255-9424.

NOVA is a production of WGBH Boston.

Major funding for NOVA is provided by the Park Foundation, dedicated to
education and quality television.

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And by the Corporation for Public Broadcasting, and by contributions to your
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